Recently, portable terminals such as smart phones and tablet terminals have become widespread. Technologies featuring user authentication techniques and screen display techniques have been developed for portable terminals and computer systems. For example, Patent Literature Document 1 discloses an authentication system built in an electronic device, which implements user authentication via a sensor used to detect a user's biological information or which implements user authentication by detecting visual or temporal input patterns. Patent Literature Document 2 discloses an image display method which automatically display a plurality of image areas on the computer screen with time differences via the Internet and which allows each user to arbitrarily carry out start display or stop display. Patent Literature Document 3 discloses a state transition determination program in ejecting an authentication device, which shows the locking of a computer upon detecting ejection of an authentication device while displaying an unlock screen. Patent Literature Document 4 discloses an Internet advertisement system using a monitor including a main screen and an auxiliary screen, wherein a main screen is displayed to show the main processing content of a user's program while an auxiliary screen is displayed to link a web page, a media display, and an operating environment display of a user's computer. Patent Literature Document 5 discloses a method and a device for protecting controls in graphic user interfaces (GUI) in a computer system, in which a protection shield or a cover is automatically eliminated from a control area when a user operates a protection icon to input a user's name and a password via an authentication box. Patent Literature Document 6 discloses a security protection method of a terminal device, in which a password store area and security state store area storing a locked or unlocked state are stored in an EEPROM of a terminal device.
Some portable terminals having touch panels may implement a locking function which limits an input operation to prevent a user's erroneous operation. For example, a lock screen displaying an unlock icon is displayed on the touch panel of a terminal in a locked state (i.e. a state to demonstrate a locking function). The terminal release the locked state when a user moves an unlock icon to a specific position on the touch panel. In the locked state, a user can recognize the present time without performing any operation to release the locked state in the terminal which displays the present time and the standby screen.